Just curious, this is a system that was used in the 1jz and 2jz with the bucket lifters and 24 valves. How come is not part of the game?

The JZ family uses DOHC (not OHV, lol) and, devs please correct me if I’m wrong, Automation uses the direct actuation method for the valves (shims and buckets). This is why, should you invest heavily in DAOHC early on, you earn familiarity in DOHC as well.

OHV is the other name for Pushrod and is used to differentiate from the Flathead, basically side-valve, version of pushrod engine designs. Both engines have their cam in the block and operate their valves via metal rods (pushrods, lol).

DOHC can also actuate their valves via rockers (solid or roller type) like the SOHC engines in-game but, to reduce redundancy and extra work for the devs (for no gameplay benefit BTW) only the direct actuation method is used in-game.

Hopefully this satisfies your curiosity and I look forward to your quasi-JZ powered creations appearing on the forums in the near future!